Percussion type rock bit



1958 w. J. BECKHAM 2,819,041

- PERCUSSION TYPE ROCK BIT Filed Feb. 24, 1953 3 Sheets-Sheet l Wz/hamBeck/7am INVENTOR.

QMQFW A TTORNE Y Jan. 7, 1958 w. J. BECKHAM 2,819,041

PERCUSSION TYPE ROCK BIT Filed Feb. 24, 1953 3 Sheets-Sheet 2 A TTORNEY7, 1958 I w. J. BECKHAM 2,819,041

PERCUSSION TYPEROCK BIT Filed Feb. 24, 1953 89 3 Sheets-Sheet 3 Q Q 5/ I6 85 W////am uf Bea/(ham K INVENTOR. 6) Y M 6 fiw' United States Patent2, 819,041 PERCUSSION TYPEROCK BIT William J. Beckham, Houston, Tex.

13 Claims. (Cl. 255-44 This invention relates to well drills, and moreparticularly to roller bits in which the cutting action is aided by animpact or percussion member.

Roller bits are frequently referred to as rock bits because they aredesigned to cut through relatively hard formations in the earths strata,such as hard limestone and other rock, rather than soft formations suchas shale and sand. The teeth on the rollers gradually wear or cut awaythe formation, but in hard rock the drilling rate is slow. Whenconventional bits rather than rock bits are used for drilling hard rock,it is necessary to provide an impact or percussion member to strike therock formation at the bottom of the hole or to strike the bit itself.

This impact member or hammer'must strike hard enough and fast enough tochip the rock at a relatively rapid rate for the conventional bit tomake progress. Thecombimtion of a percussion member with a roller orrock bit provides the best known means for drilling through extremelyhard strata, however, as the cutters rapidly break the rock chipped bythe impact member into particles which are small enough to be carried upthe bore hole by the drilling mud.

' Prior to my invention most percussion type bits have utilized airpressure, mud pressure, or water pressure supplied from the surface tooperate the hammer members. Some few, moreover, have utilized thedifference in rotational travel between the drill pipe and the bit, whenthe bit has encountered a hard formation, to wind up and release theimpact device. While each of these means of operating the impact plungerhas had a limited success, none have been completely satisfactory.

Consequently, it is an object of my'inventon to combine a rock bit withan impact member in such a manner that the impact member is actuated inresponse to rotation of the cutters.

It is another object of my invention to provide a new A still furtherobject of my invention is to provide a novel arrangement of hydraulicmotor means, operated in response to rotation of the bit cutters, forbuilding upthe necessary hydraulic pressure for operating the percussionmember. I

In carrying out my invention in a presently preferred form I utilize arock drill bit of the type designed for use with oil well rotarydrilling units in which the drill pipe is rotated by a rotary table.comprise three cone shaped steel cutters supported on bearings carriedby the bottom portion of the bit body or frame. These cutters are of thestandard type used in Such bits generally drilling through extremelyhard formation, which serve to cut the walls and bottom of the hole,pulverizing the rock into small particles. My invention improves theaction of such standard rock bit cutters, however, by providing meansoperated by the rotation of one or more of the cutters for actuating apercussion member.

My operating means for the impact member preferably comprises ahydraulic actuator including, in the frame of thedrill bit, acylinderdisposed above each cutter. Reciprocably mounted in each cylinder is apiston operated by rotation of the cutter; for example, the piston mayhave a rod connected to it which is associated with one or more camsformed on or attached to the free end of the cutter shaft. As the weightof the drill pipe is carried by the cutters, suflicient force becomesavailable at each cutter, upon rotation of the drill stem and thecutters by the rotary table, to actuate one or more small pistons toproduce considerable hydraulic pressure.

As the cone cutters rotate the small pistons are reciprocated thereby topump a stream of oil into a large master cylinder, preferably located inthe center of the drill bit frame. This flow of oil serves to build uppressure beneath a piston in the master cylinder, which pressure willmove the piston upwardly against the bias of a spring or other suitableresisting force. The spring, in effect, stores the energy appliedbeneath the piston until a predetermined spring force is attainedwhereupon, by the action of a relief valve, the pressure below thepiston is suddenly reduced. Immediately the restraining spring drivesthe piston downwardly until the plunger or impact member carried by thepiston strikes against the hard formation at the bottom of the hole,chipping and breaking it so that the cutters can more effectively andrapidly pulverize the formation.

I provide suitable ports in my drill bit for the introduction ofdrilling mud and washing water at the bottom of the bit, and providesuitable means such as a reservoir in the bit frame for supplying aproper liquid for use in the hydraulic system. The plunger operatingmechanism is protected from contact with the drilling mud and washingwater by the drill casing, so that only the hydraulic fluid comes intocontact with the moving parts.

While the features of my invention which I believe to be novel are setforth with particularity in the appended claims, my invention itself,both as to its organization and method of operation, together withfurther objects and advantages thereof, may best be understood byreference to the following description taken in connection with theaccompanying drawings. In these drawings Fig. 1 is a sectional elevationview through the longitudinal axis of my drill bit, showing the plungerin retracted position; Fig. 2 is a section looking along the lines 2-2of Fig. 1; Fig. 3 is a section looking along the lines 3-3 of Fig. 1;Fig. 4 is a view similar to Fig. l but showing the plunger in its impactposition; Fig. 5 is an enlarged sectional elevation of the smallhydraulic cylinder and related structure shown in Fig. 1; Fig. 6 is anenlarged sectional side view of the valve mechanism for controlling themaster cylinder, as shown in Fig. 1; Fig. 7 is a side elevation of thevalve device of Fig. 6; and Fig. 8 is a plan view of the valve device ofFig. 6.

Referring now to Fig. l of the drawings I have shown a sectional viewthrough the body or frame 1 of my drill bit, in which one of a pluralityof cone-shaped steel cutters 2 can be seen along with one of a pluralityof scraper members 3. It will be understood that three cutters spacedequiangularly around the circumference of the bit frame and threesimilarly spaced scrapers are used in the preferred form of myinvention. The bit preferably includes a cap portion 4 attached to theframe by means of bolts or screws 5, which cap has a threaded upper end6 suitable for attachment to the end of the drill pipe in theconventional manner. The frame 1 forms a chamber 7 which serves as areservoir for hydraulic liquid as well as housing a part of the impactoperating mechanism. It may be filled to the level indicated either byremoving the cap 4 or by utilizing an opening, not shown, in theframe 1. The impact mechanism itself includes a piston 8 within thechamber 7 operatively connected to a plunger or hammer 9, and having ahardened steel cap 10 screwed or otherwise attached thereto. In order topermit washing in the vicinity of the impact member and bit cutters, andto provide drilling mud to the bottom of the hole, I further provide apassageway 11 in the frame 1 communicating between the end 6 of theframe cap and the bottom of the bit.

It should be understood in considering the following description thateach hydraulic pressure mechanism is preferably identical, and that thesingle mechanism shown and described in relation to its cutter istypical and illustrates the construction of each of the others.

The cutter 2 is non-rotatably mounted on a shaft or pin 12 which isjournaled in suitable .bearings 13 and 13a carried by the bit frame.Usually ball or roller bearings are employed for this purpose.Non-rotatably mounted on the shaft 12 is a cam 14 which has at least oneand preferably three lobes 15. Consequently, upon rotation of the drillpipe, the bit frame rotates by virtue of the direct connection throughthe end portion 6 of the cap 5. The cutter 2 then rotates at about twicethe speed, measured in revolutions, of the drill pipe, the exact ratiodepending on the relative diameters of the bit frame and the cutter.Thus with a drill pipe or stem rotation of sixty revolutions per minute;the cutter may be driven at approximately one hundred and twentyrevolutions per minute. The use of a plurality of cam lobes on the cam,which rotates with the cutter as a unit, further multiplies therotational velocity in a manner explained hereinafter.

In order to provide hydraulic pressure for actuating the percussionmember 9, I utilize the rotation of the cam 14 to drive a smallhydraulic piston 16. The piston 16 is reciprocated within a cylinder 17in the bit frame and forms a seal with the cylinder inner wall by meansof piston rings 18, which may for example, be of neoprene. A roller typecam follower 19 is carried on the lower end of a rod 20, which isconnected to the bottom of the piston, engages the surface of the cam 14so that the piston is driven upwardly within the cylinder upon contactwith each of the three cam lobes 15. Thus the piston will bereciprocated three times for each revolution of the cutter. The cam rod20 is slidably mounted in the frame 1 and passes through an opening in aplate 21, which forms the bottom of the cylinder 17, to connect with thepiston 16. It is spring biased to a downward position by means of a coilspring 22 which bears at its upper end against the plate 21 and at itslower end against a plate 23, which in turn is supported on a nut 24.The nut 24 serves not only to support the plate 23 so that the cam rod20 will be biased downwardly, but also serves to provide adjustmentmeans by which the compression of the spring 22 can be varied. In thismanner the cam follower roller 19 will be kept in contact with thesurface of the cam 14 at all times.

As best shown in Fig. 5 there is an intake passage 25, in the upper endof the cylinder 17, preferably formed by use of a threaded nipple 26which is screwed into the top of the cylinder. There is also a dischargepassageway 27 at the upper end of the cylinder 17 which may be formed bya threaded nipple 28 adjacent the intake passage 25. At the upper end ofthe nipple 26 is a one way valve 29 which permits flow into thepassageway in the direction of the cylinder, but prevents reverse flow.The valve 29 comprises a body or casing 30 which may be screwed onto theupper end of the nipple 26. The casing 30 has a central passageway andserves as a housing for a bushing 31 which constitutes a guide bearingfor a slidable valve stem 32. The valve stem 32 has mounted on its upperend a tapered valve element 33 adapted to fit a valve seat 34 formed inthe body 30. The valve element 33 is urged upwardly by a spring 35 orother suitable means, so that it is normally closed against the passageof fluid through the central passageway of the valve body 30. The valvestem guide bushing 31, moreover, is provided with a plurality ofpassageways 36 through which hydraulic liquid can flow when the valveelement 33 unseats. The springs 22 and 35 should be selected of suchsize and spring constants that the restraining force on the valve member33 is small compared to the downward bias on the piston 16, so that upondownward travel of the piston the pressure difierential created will besuflicient to unseat the valve, as explained more fully below.

While not essential to the utilization of my invention it is highlydesirable to provide an oil strainer 37 which may, for example, becarried on the upper end of the valve casing in the manner shown in Fig.5, by screwing an integral nipple formed on the lower end of thestrainer into the upper end of the casing. The liquid flowing to thecylinder must then pass through the strainer and its depending nippleportion and through the central passageway in the valve body 30. Uponeach downward stroke of the piston 16, in response to the urging of thespring 22, as soon as the reduction in pressure below the movable valvemember 33 becomes sufficient to create a pressure differential acrossthe valve member great enough to overcome the bias of the relativelyweak spring 35, the valve 29 will pass hydraulic oil from .the strainer37 to the interior of the cylinder 17.

It will be understood, of course, that suitable means will be providedfor lubricating the moving parts, as by supplying hydraulic oil to themfrom the reservoir 7. For example a groove 38 in the outer threaded wallof the cylinder 17 and a slot 39 in the portion of the frame 1surrounding the cam rod may be provided to lubricate the cam surface,cam follower, and cutter bearing. Moreover, the cam rod may beconveniently held against roa tation, relative to the frame 1, by meansof a key 40 slidably movable within the slot 39.

When any one of the cam lobes 15 come into contact with the cam follower19, the cam rod 20 and consequently the piston 16 are driven upwardly,thereby presssurizing the liquid previously drawn into the cylinder.This increase in pressure securely seats the valve member 33 to preventfluid from flowing through the valve 29. Consequently, as the pistoncontinues its upward movement the fluid is forced instead through thedischarge passageway 27 into a suitable conduit such as the hose 41.This hose may be coupled to the discharge nipple 28 by means of acoupling bracket 42. As best shown in Fig. 1 taken in connection withFig. 3 the hydraulic fluid flows through the hose 41 into a one wayvalve 43 which preferably is of identical construction to that of thevalve 29. In other words the valve 43 permits the flow of hydraulicfluid through it from the cylinder 17, but seats in response to fluidpressure at its discharge side and the pressure of its own spring toprevent reverse flow. A hose 44 extends from the discharge side of thevalve 43 to a header 45 having intakes 46, 47 and 48, respectively, toaccommodate the hose connections from each of the hydraulic cylindermeans. It will be understood, of course, that each hose has a valvesimilar to the valve 43. The header 45 in addition has a dischargepassageway 49 communicating with a cylinder 50 in which the masterpiston reciprocates. In the form shown, a tapered fitting 51 with an oilpassage through it is provided in the bottom of the cylinder 50, and theheader 43 is attached to it, preferably by a threaded connection. Thusfitting 51 forms the passage 49.

In the initial setting of the cutters, the cams are preferclosed. Thisis not essential, however, as my hydraulic system will function properlywithout precise timing of the small pistons and even if all threepistons are operated simultaneously, as may become the case in actualdrilling practice. Whenever the pressure in a hose line 7 between asmall cylinder and its valve falls below the pressure in the header 45,that valve will close because of its one-way construction,'and hydraulicliquid will not begin reverse flow. 'On the other hand so long as thispressure exceeds that of the header, there will be no tendency towardreverse flow. Consequently my hydraulic .motor means is not dependentupon the timing of the cutter operated pistons.

As previously explained the piston 8 is adapted to reciprocate withinthe cylinder 50, being driven upwardly in the cylinder in response to abuild up of liquid pr ssure beneath it. This piston may be provided withpiston rings 52 of any suitable material, such as neoprene. Also aspreviously explained a plunger 9 is connected to the bottom of thepiston 8 for sliding movement in a passageway formed in the frame 1 ofthe bit. Near its upper end the plunger may be guided during itsreciprocation by a bushing portion 53 formed on the bottom on thecylinder 50. This bushing portion of the cylinder serves not only toguide the plunger but may be secured in threaded engagement with the bitframe to fix the cylinder 50 in position within the chamber 7. Theplunger is further guided by the central bore in the bit frame, and aseal 54 is provided near the lower end to prevent the oil or otherhydraulic liquid, passing into the bore from the cylinder, fromescaping. The seal may advantageously be held in a cap 55 screwed intothe bit frame. In such an arrangement the seal is pressed into a recessin the cap, and the cap is provided with a central passageway toaccommodate the plunger.

In order effectively to utilize the hydraulic pressures developed by thesmall piston and cylinder arrangements to operate the plunger or striker9, I provide a control valve 56 which serves as a quick opening reliefvalve and time delay device to permit rapid and substantially completeexhaustion of the pressure beneath the piston 8. I provide fluidpressure to the control valve 56 through a plurality of ports 57formed-in the piston 8, which serve to deliver a portion of thehydraulic oil in the cylinder 50 to the control valve mechanism. As willbe explained more fully hereinafter a passageway 58 leads from the ports57 to the control valve 56, which passageway must become filled withhydraulic oil before hydraulic pressure will begin to build up beneaththe piston 8. Thereafter additional oil supplied to the cylinder 50 willcause a rapid rise of fiuid pressure whereupon the piston Will be movedupwardly as'the first step toward causing the impact member 9 to delivera blow to the formation being drilled.

One convenient means of forming the passageway '8, as well as supportingthe valve 56, is shown in Figs. 1 and 4. A bushing 59 having a threadedlower end is screwed into a central recess in the piston 8, whichcentral recess communicates with the ports 57. The upper end of thebushing 59 forms a shoulder 60 which has several functions as' will beexplained later in the specification. The passage 58 may be reduced incross section near the upper end of the bushing 59 to receive thethreaded lower end portion of a body 61 which houses the valve 56. Inthis manner both the bushing 59 and the valve 56 are carried by andfixed to the piston 8, so they will move up and down in response topiston movement. Moreover, as is evident from an inspection of Fig. l orFig. 4 the piston 8 will move upwardly in response to continued deliveryof hydraulic oil under pressure from the small cylinders so long as thevalve 56 does not pass any appreciable amount of oil. Upon opening ofthe valve 56, however, the pressure in the passage 58 and consequentlyin the space within the cylinder below the piston 8 will be relieved sothat no further upward forces of any consequence will be acting on thepiston. Moreover, by making the passage through the valve 56 ofsulficient diameter to readily accommodate the flow from the dischargeopening 49, of the header- 45; and by making the total cross sectionalarea of the ports 57 at least as large, there will then be nosubstantial forces, other than friction, tending to prevent the piston 8from returning to the bottom of the cylinder 50. As it is obviouslydesirable that the plunger 9 strike the bottom of the formation with arelatively large striking force, I provide a spring 62 between theflange and the cap 4. This spring may be held in place on the flange 60of the bushing 59 by means of a plurality of curved straps 63 and may beheld in place beneath the cap 4 by means of a plurality of cleats 64.The straps 63 and the cleats 64 may be suitably attached to the flange60 and the cap 4 by means of nuts and screws respectively. The spring 62is of such a length that, when the valve 56 opens to permit the piston 8to move downwardly, it will support the piston to prevent it fromstriking the bottom of the cylinder. This not only avoids striking thetop of the fitting 51 but prevents any other sharp impact which woulddecrease the life of the parts.

Since the length of travel of the piston within the cylinder 50 islimited by space requirements to approximately two inches, I prefer touse a main spring having a constant in the order of two thousand poundsper inch, so that upon full upward travel of the piston aforce in theorder of four thousand pounds will be stored for later utilization indriving the plunger or striker 9 downwardly against the hard formationat the bottom of the hole. The amount of pressure required to bedeveloped in the cylinder 50 below the piston 8 will depend, of course,on the effective area of the piston. It has been found, moreover, thatby the use of relatively small pistons in conjunction with the cuttersthat pressures in the order of one thousand pounds per square inch canbe readily developed. The pressure at which the valve 56 will open ispreset at a calculated figure dependent on the effective piston area,usually about seven or eight hundred pounds per square inch, so that thedesired amount of force will be stored in the spring before the pressurein the cylinder 50 is released to permit the spring pressure to drivethe plunger downwardly.

I provide guide means for the spring 62 comprising a plurality of rods65 attached to the flange 60 just within the circle formed by the bottomcoil of the spring. Each rod 65 is positioned so that its upper or freeend enters into the lower end of one of several tubes 66 attached to thebottom of the bit frame cap 4. The upper end of the rod 65 just barelyenters the lower end of the tube 66 when the piston is in the positionshown in Fig. 4, but approximately two inches of the rod 65 slidesupwardly into the tube 66 during the upward travel of the piston 8.While not essential to the operation of my hydraulic mechanism, thisguide arrangement serves to prevent any tendency of the spring 62, orthe bushing 59, to' tilt, thereby preventing unnecessary strain on thepiston 8 and cylinder 58 in maintaining correct alignment.

While any suitable control valve which will open in response to apredetermined pressure and will remain open for a predetermined timeinterval after relief of such pressure would be suitable, I have shown anovel control valve especially adapted for use with my percussion typerock bit. This valve will be better understood if the followingdescription is taken in conjunction with Figs. 6, 7 and 8.

Extending about half way up from the bottom through the body 60 of thevalve 56 is a vertical passage 67 opening into a horizontal passage 68.The vertical passage 67 is blocked at its upper end by a plug member 69and the horizontal passage 68 may be closed by a movable valve member70. The movable valve member or flapper 70 is pivotally mounted onthe-valve body 60 by means of a pin 71, and may swing from a closedposition to an open position of as much as thirty degrees, for example,from the vertical. The flapper 70 is adapted to seat against a valveseat or face 72 formed in the body 60. The flapper may be tapered formatching engagement with the face 72 and may further be provided with asuitable seal 73 to further insure against leakage. The seal ring 73 ispreferably recessed in a slot portion 74 of the flapper so that thetapered portion can fit snugly against the face 72 when the flapper isfully closed and the ring 73 compressed in sealing engagement with saidface. This portion of my valve is entirely conventional and any suitableclosure member and seal may be used in carrying out my invention.

Turning now to the control portion of the valve 56, the plug 69 isprovided with a small orifice 75 communicating between the passage 67and the lower portion of a passage 76, also within the valve body. Thelatter passage 76 serves as a cylinder within which a control piston v77 may reciprocate. This control piston 77 is provided with an enlar edpiston head portion having suitable piston rings 78 adapted to sealagainst the cylinder wall. The orifice 75 permits the flow of fluid fromthe master cylinder 50 and the passageways 58 and 67 into the cyl---' 7ing of the flapper 70, as will be more fully explained.

As shown in Figs. 7 and 8 the upward movement of the piston 77 isopposed by the bias of a pair of springs 79 carried on a pair of rods 80substantially parallel to the control piston and also slidable withinthe valve body 60. These rods 80, which serve primarily as valve closuremembers, bear against a yoke 81 riveted or otherwise suitably attachedto the back of the flapper 70. It is preferable that the connectionbetween the rods 80 and the yoke 81 be through a cushioning arm member82, as best seen in Fig. 7, which member is pivotally connected to abase portion 83 of the yoke. Pressure exerted by the rods 80 upon thepivoted arm 82 is transferred to the main portion of the yoke 81 bymeans of a pair of springs 84, the upper ends of which bear against thearm 82 and the lower ends of which bear against a projection 85 of theyoke. The springs 84 are kept in position by means of pins 86 and 87respectively attached to the arms 82 and the projections 85.Consequently, the engagement by the rods 80 with the arms 82 biases theflapper 70 toward its closed position.

As previously explained the rods 80 carry springs 79, and these springsapply pressure for normally keeping the rods in engagement with the arms82. These springs 79 bear at their lower ends against integral flangepor tions 88 on the rods and each bears at its upper end against anadjusting screw 89. Each screw 89 may be provided with a central opening99 therethrough to accommodate the upper end of the rod 80 with which itis associated, thereby to permit full upward movement of the rod in amanner to be further described. Each of the pair of screws 89 issupported in the upper portion of the valve body 60 and may be adjustedto varythe initial spring compression in order to predeterrnine theforce necessary to move the rods 80 out of their valve closure position.This, moreover, predeterrnines the amount of force necessary to elevatethe control piston 77, as a pin 91, extending through the control piston77, attaches it to the rods 80 at their respective shoulder portions 88.Consequently, the combined spring forces of the two springs 79 act toresiliently oppose upward travel of the control piston. By proper choiceof the spring constant for the springs 79, and by adjustment of thescrews 89, the hydraulic pressure necessary to move the control piston77 the desired distance for permitting opening of the flapper 70, whichequals the previously mentioned pop-off pressure, is accuratelypredetermined.

To hold the flapper 70 in its closed position against the hydraulicpressure in the passages 67 and 68 -I provide a latch 92 slidablymounted in the valve body and engageahle with the back of the topportion of the flapper. The

engaging surfaces of the latch and flapper are preferably beveled sothat upon downward movement of the latch 92 these surfaces will providea cam action to force the flapper tightly against the valve seat. Anelongated slot 93 is provided in the upper portion of the latch 92; Thisslot receives a pin 94 carried by an arm 95, which in turn is pivotallymounted on a pin 96 carried by the valve body 60. The arm 95 is providedto control the position of the latch 92, including both elevating it tofree the flapper to permit it to open in response to hydraulic pressure,and forcing it downwardly to latch the flapper in its closed position.This latch actuating arm 95 is forked at its free end so as to form ayoke through which the upper end of the latch passes. The pin 94 isinserted between the two prongs of the arm 95 and, as previouslyexplained, passes through the slot 93 in the latch. The slot, however,is sufficiently elongated that considerable free play or lost motion ispermitted before the pin 94 will begin to move the latch.

The latch actuating arm 95 is itself operated by movement of the controlpiston 77, which is provided with a slot 97 through which the arm 95extends. Consequently, movement of the control piston provides a forceacting on a lever arm equal the distance from the piston to the pin 96,which force moves the arm 95 in the same direction as the piston travel.The pin 94 at the free end of the arm 95 travels an effective distancegreater than the movement of the piston 77 in a ratio equal to the ratioof the distance between it and the pin 96 compared to the efiectivelever arm between the piston and the pin 96. When the pin 94 reaches theupper end of the slot 93, further upward movement of the piston willelevate the latch 92 to free the flapper 70. The opposite is true, ofcourse, upon downward movement of the piston.

The operation of the valve 56 is relatively simple, yet very effective.It is best understood, moreover, when described in conjunction with theoperation of the entire percussion type rock bit. As previouslyexplained rotation of the drill pipe causes rotation of the bit frame 1,which in turn causes the cutter 2 to rotate on its axis and cuts andcrushes the formation beneath it, under pressure impressed upon it bythe weight of the drill pipe itself. This rotation is translated into anupward stroke of the small piston 16 each time a cam lobe 15 comes intoengagement with the cam follower wheel 19. Each upward stroke forces asmall amount of hydraulic liquid through the header 45 into the mastercylinder 50. Since the valve 56 is initially closed, successiveoperations of the pistons 16 serve to fill the space below the mainpiston 8 within the cylinder 50, the passage 58, and the passage 67. Assoon as sufficient pressure builds up in the cylinder 50 to overcome theforce of the spring 62, the main piston 8 begins its upward travel,compressing the spring 62 and storing a return force therein.

The pressure for elevating the piston 8 also causes the valve controlpiston 77 to move upwardly, in opposition to the bias of the springs 79.This upward movement carries with it the valve closure rods 80, therebyrelieving the pressure on the yoke 81 which has hitherto tended tooppose opening of the flapper 70. The flapper does not immediately open,however, as the latch 92 prevents it from moving. When the pin 94,however, has been moved upwardly by the piston 77 the entire length ofthe slot 93, further upward travel of the control piston 77 willwithdraw the latch 92 from engagement with the flapper 70, and theflapper will immediately open,

thereby permitting almost immediate release of the pressure within thevalve passages 67 and 68 and within the cylinder 50. The extent ofopening of the flapper 70 is controlled only by the distance which theflapper. closure rods 80 have been elevated by the piston movement,as-contact between these rods and the arms 82 will cause compression ofthe spring 84 even to the extent of permitting the guides '86 and 87 toabut or aiternately to permit the spring to close completely, ifnecessary, to limit further travel of the flapper. This relieves thepressure below the piston 8 and permits the spring 62 to drive thepiston downwardly, causing sharp impact between the cap 10 carried onthe plunger 9 and the formation at the bottom of the hole. This willchip away part of the formation, which-chips will be moved by thescrapers 3 into the path of the cutters 2, whereupon they will becrushed and broken into smaller particles and carried away in the mudstream.

The valve 56 inherently provides a time delay device to prevent anysubstantial closing of the flappers 70 during the downward movement ofthe piston 8. This is desirable to prevent any substantial back pressurefrom building up beneath the piston in response to delivery of hydraulicliquid thereto by the continued operation of the small pistons 16. Thistime delay feature is provided by the orifice 75 which, thoughpermitting exhaustion of the pressure beneath the control piston 77within the cylinder 76 after opening of the flapper, so throttles theflow of hydraulic liquid that the piston cannot immediately return toits lower position. Therefore the rods 80 are maintained at a suflicientheighth that they will not close the flapper until after the plunger 9has completed its impact stroke. As the pressure in the cylinder 76below the piston 77 is gradually reduced, the piston 77 is returned toits lower position in response to the urging of the springs 79. As thisdownward stroke begins, the rods 80 begin their downward movement forthe purpose of closing the flapper. Because of the length of the slot 93the latch 92 will not be forced downwardly until the rods 80 havesubstantially closed the flapper, and this latch will therefore remainin its elevated'position because of the friction between it and thevalve body. In the event the latch were to fall by gravity to its valveclosing position, it would be gently pushed out of the way by theflapper as it closed, however, so that such an event would not cause thevalve to become inoperative. As the piston 77 approaches the bottom ofthe cylinder, the valve rods exert sufii-eient pressure on the arms 82to substantially close the flapper against the valve face 72. A tightclosure is insured when the piston 77 moves the remaining distance tothe bottom of the cylinder, since the pin 94 engages the bottom of theslot 93 and drives the latch 92 into engagement with the flapper, asshown in Figs. 6, 7 and 8. The tapered leading edge of the latch camsthe flapper securely into engagement with the valve face, and the latchthereafter holds it against opening until the next upward stroke of thecontrol piston 77.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made; and I therefore contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A percussion type rotary drilling mechanism comprising a drill bitadapted to be rotated within an oil well bore hole, at least one cuttermounted on the lower end thereof for rotation on said bit duringrotation of said bit in the well bore hole, an impact member carried bysaid bit and hydraulic means operable by said cutter in response torotation of said cutter relative to said bit to actuate said impactmember whereby said impact 10 member will repeatedly strike theformation in said bore hole.

2. A percussion type rotary drilling mechanism comprising a hollowcylindrical drill bit adapted to be rotated within a bore hole, aplurality of cutters mounted on the lower end thereof for rotation onsaid bit in response to rotation of said bit, an impact plunger slidablymounted for reciprocation in said bit, said plunger being so supt ortedthat in its lowermost position it extends below said cutters, and meansincluding a fluid pressure generating unit actuated by said cutters inresponse to rotation thereof relative to said bit to operate saidplunger to cause repeated impacts against the formation at the bottom ofthe bore hole.

3. A rotary drilling mechanism comprising a drill bit adapted to berotated within a bore hole, at least one cutter rotatably mounted on thelower end of said bit for engagement with the formation at the bottom ofthe bore hole, a cam rotated in response to rotation of said cutter, acam follower reciprocated by said cam, a fluid pressure system operatedin response to reciprocation of said cam follower, said fluid pressuresystem comprising -at least one pressure generating unit and a mainoperating unit; said pressure generating unit including a pistonconnected to said cam follower, said main operating unit including apiston slidably mounted in said bit and an impact member slidablymounted in said bit and reciprocable in response to operation of saidmain unit piston, said impact member being positioned to strike thebottom hole formation upon downward movement of said main unit piston;and a passageway from said generating unit to said main operating unitto deliver fluid under pressure thereto to operate said main unitpiston.

4. A percussion type rotary drilling mechanism comprising a drill bitadapted to be rotated within a bore hole, at least one cutter rotatablymounted on the lower end of said bit for engagement with the formationat the bottom of the bore hole, a cam rotated in response to rotation ofsaid cutter, a cam follower reciprocated by said earn, a hydraulicpressure system operated in response to reciprocation of said camfollower, said hydraulic system comprising at least one pressuregenerating unit and a main operating unit; each of said pressuregenerating units having a cylinder, liquid supply means for saidcylinder a piston slidable within said cylinder to pressurize saidliquid, and a connection between said piston and said cam follower foroperating said piston; said main operating unit having a cylinder withinsaid bit and a piston operating within said cylinder, said main unitpiston carrying an impact member slidably mounted in said bit andpositioned to strike the bottom hole formation upon downward movement ofsaid main unit piston, and a passageway from said generating unit tosaid main operating unit to deliver liquid under pressure thereto tooperate said main unit piston.

5. A percussion type rotary drilling mechanism comprising a drill bitadapted to be rotated within a bore hole, at least three cuttersrotatably mounted on the lower end of said bit for engagement with theformation at the bottom of the bore hole, a separate cam connected toeach of said cutters, a separate cam follower engageable with each ofsaid cams, a hydraulic pressure system operated in response toreciprocation of said cam followers, said hydraulic system comprising apressure generating unit for each cam follower and a single mainoperating unit; each of said pressure generating units having acylinder, liquid supply means for said cylinder a piston slidable withinsaid cylinder to pressurize said liquid, and a connection between saidpiston and said cam follower for operating said piston; said mainoperating unit having a cylinder within said bit and a piston operatingwithin said cylinder, said main unit piston carrying an impact memberslidably mounted in said bit and positioned to strike the bottom holeformation upon downward movement of said main unit piston, and apassageway from said gencrating units through a common header to saidmain operating unit to deliver liquid under pressure thereto to operatesaid main unit piston.

6. In a rotary drilling mechanism of the type used in drilling throughhard formations at the bottom of bore holes, having a drill bit withrotatably mounted cutters thereon and an impact member associatedtherewith, the improvement in means for operating said impact membercomprising: reciprocable means operated by rotation of oneof saidcutters, a hydraulic system operated in response to'movement of saidreciprocable means for actuating said impact member, said hydraulicsystem comprising a pressure generating unit and a main operating unit,liquid supply means for said pressure generating unit, a piston in saidmain operating unit, said piston being connected to said impact member,conduit means from said generating unit to said main operating unit fordelivery of liquid under pressure thereto to elevate said piston, biasing means opposing elevation of said piston and exerting a restoringforce downwardly thereon in opposition to the pressure of the liquid,and a control valve operable to relieve the pressure in said ,rnainoperating unit to initiate a downward stroke of said piston.

7. In a rotary drilling mechanism adapted for drilling the formation atthe bottom of a bore hole, having a drill bitwith rotatably mountedcutters thereon and a percussion member associated therewith, theimprovement in means for operating said percussion member comprising: ahydraulic system operated in response to rotation of at least one ofsaid cutters, said hydraulic system comprisin a pressure generating unitand a main operating unit; said generating unit having a cylinder,liquid supply means for said cylinder, a pistoh, and means operated byrotation of one of said cutters for reciprocating said piston Withinsaid cylinder; said main operating unit having a main cylinder, a mainpiston within said main cyl inder and connected to said percussionmember, conduit means from said generating unit cylinder to said maincylinder for delivery of hydraulic liquid under pres sure thereto toelevate said main piston, biasing means opposing elevation of said mainpiston and exerting a restoring force downwardly thereon in oppositionto the hydraulic pressure, and a control valve operable to relieve saidhydraulic pressure in said main cylinder.

8. In a rotary drilling mechanism adapted for drilling the formation atthe bottom of a bore hole, having a drill bit with rotatably mountedcutters thereon and a percussion member associated therewith, theimprovement in means for operating said percussion member comprising: acam rotated in response to rotation of one of said cutters, a camfollower for said cam, a hydraulic system operated in response toreciprocation of said cam follower by said cam for actuating saidpercussion member, said hydraulic system comprising a reservoir forliquid within said bit, a pressure generating unit communicating withsaid reservoir, and a main operating unit; said generating unit having acylinder, a piston within said cylinder, and means connecting saidpiston to said cam follower for reciprocating said piston; said meansoperating unit having a main cylinder, a main piston within said maincylinder and connected to said percussion member, conduit means fromsaid generating unit cylinder to said main cylinder for delivery ofhydraulic liquid under pressure thereto to elevate said main piston,biasing means opposing elevation of said main piston and exerting arestoring force downwardly thereon in opposition to the hydraulicpressure, and a control valve operable in response to the build-up of apredetermined restoring force to relieve said hydraulic pressure in saidmain cylinder.

9. In a rotary drilling mechanism of the type employed in drilling hardformations at the bottom of bore holes, having a drill bit withrotatably mounted cutters thereon and a percussion member associatedtherewith, the improvement in means for operating said percussion membercomprising: a cam rotated in response to rotation of one of saidcutters, a cam follower for said cam, a fluid pressure system foractuating said percussion member operated in response to reciprocationof said cam follower by said cam, said fluid pressure system comprisinga pressure generating unit, a main operating unit, and a source of fluidfor supplying said pressure generating unit; said main operating unitincluding a piston operatively connected to said percussion member; apassageway from said generating unit to said main operating unit fordelivery of fl-uid under pressure thereto to elevate said piston,biasing means opposing elevation of said piston and exerting a restoringforce downwardly thereon in opposition to the fluid pressure, and acontrol valve adapted to open inresponse to the build-up of apredetermined fiuid pressure in said main operating unit to relieve thepressure therein, said control valve having time delay means preventingclosing during the downward stroke of said piston.

10. In a rotary drilling mechanism adapted for drilling the formation atthe bottom of a bore hole, having a drill bit with rotatably mountedcutters thereon and a percussion member associated therewith, theimprovement in means for operating said percussion member comprising: acam rotated in response to rotation of one of said cutters, a camfollower for said cam, a hydraulic system operated in response toreciprocation of said cam follower by said cam for actuating saidpercussion member, said hydraulic system comprising a liquid reservoirwithin said bit, a pressure generating unit communicating with saidreservoir, and a main operating unit; a piston in said main operatingunit, said piston being connected to said percussion member, apassageway from said generating unit to said main operating unit fordelivery of hydraulic liquid under pressure thereto to elevate saidpiston, spring means opposing elevation of said piston and exerting arestoring force downwardly thereon in opposition to the hydraulicpressure, and a control valve carried on said piston operable to relievesaid hydraulic pressure in said main operating unit to initiate adownward stroke of said piston.

ll. Ina rotary drilling mechanism adapted for drilling the formation atthe bottom of a bore hole, having a drill bit with rotatably mountedcutters thereon and an impact plunger associated therewith, theimprovement in means for operating said impact plunger comprising: a camrotated in response to rotation of one of said cutters, a cam followerfor said cam, a hydraulic system operated in response to reciprocationof said cam follower by said cam for actuating said plunger, saidhydraulic system comprising a pressure generating unit and a mainoperating unit; said generating unit having a cylinder, liquid supplymeans for said cylinder, a piston, and means connecting said piston tosaid cam follower for reciprocating said piston within said cylinder;said main operating unit having a main cylinder, a main piston withinsaid main cylinder and connected to said plunger, conduit means fromsaid generating unit cylinder to said main cylinder for delivery ofhydraulic liquid under pressure thereto to elevate said main piston,spring means opposing elevation of said main piston and exerting arestoring force thereon in opposition to the hydraulic pressure, and acontrol valve operable to relieve said hydraulic pressure in said maincylinder whereby said spring means drive said piston and plungerdownwardly.

12. In a rotary drilling device having a drill bit with a rotatablymounted cutter thereon and an impact plunger associated therewith, theimprovement in means for operating said impact plunger comprising: ahydraulic system operated in response to rotation of said cutter, apiston operatively connected to said plunger and adapted to be elevatedin response to hydraulic pressure, biasing means opposing elevation ofsaid piston and exerting a restoring force downwardly thereon inopposition to the hydraulic pressure and a control valve operable inresponse to a predeterminedhydraulic pressure to relieve said hydraulicpressure; said control valve comprising a fluid inlet, a fluid outlet,closure means releasably closing said fluid outlet, a latch holding saidclosure means in its closed position, means operable in response to saidhydraulic pressure to remove said latch, and time delay means preventingthe return of said latch for a predetermined period.

13. A percussion type rotary drilling bit comprising a hollow bodyadapted to be rotated within a well bore to perform a drillingoperation, a cutter rotatably mounted on the lower end of said body forrotation relative thereto in response to rotation of said body duringthe drilling operation, a percussion plunger slidably mounted for axialreciprocating movement within said body, said plunger 14 being movableupon actuation thereof to strike the bottom of the well bore, and meansoperated by the cutter in response to rotation thereof to intermittentlyactuate said percussion plunger.

References Cited in the file of this patent UNITED STATES PATENTS1,861,042 Zublin May 31, 1932 2,033,527 Kitching Mar. 10, 1936 2,234,798Craig Mar. 11, 1941 2,241,712 McNamara May 13, 1941 2,324,552 BaileyJuly 20, 1943 2,563,083 Topanelian Aug. 7, 1951 U. S. DEPARTMENT OFCOMMERCE PATENT OFFICE CERTIFICTE F CDRCTIN William J, Beokham.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should. read as corrected below.a

Column '7, line 34, before the Word "moved" strike out J'been"; columnll, line 59, for "said means operating read W said. main operatingSigned and sealed this let clay of April 1958,

(SEAL) Atteet:

KARL HO AXLINE ROBERT c. WATSGN Attesting Officer Gonmissioner ofPatents

